Derivation of the spin Hamiltonians for Fe in MgO

• Autores: Ferron, Alejandro; Delgado, Fernando; Ferández Rossier, Joaquín
• Año de publicación: 2015
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: DENSITY FUNCTIONAL THEORY; MgO; CI; ELECTRONIC AND MAGNETIC PROPERTIES; SPIN HAMILTONIAN; WANNIER; MAGNETIC TUNNEL JUNCTION
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

A method to calculate the effective spin Hamiltonian for a transition metal impurity in a non-magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. In the first step we calculate the electronic structure employing standard density functional theory (DFT), based on generalized gradient approximation (GGA), using plane waves as a basis set. The corresponding basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The third step is to solve, by exact numerical diagonalization, the N electron problem in the open shell of the magnetic atom, including both effects of spin–orbit and Coulomb repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can also include the orbital angular momentum L when appropriate. We successfully apply the method to Fe in MgO, considering both the undistorted and Jahn–Teller (JT) distorted cases. Implications for the influence of Fe impurities on the performance of magnetic tunnel junctions based on MgO are discussed.
Fil: Ferron, Alejandro. International Iberian Nanotechnology Laboratory; Portugal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnologica; Argentina
Fil: Delgado, Fernando. International Iberian Nanotechnology Laboratory; Portugal
Fil: Ferández Rossier, Joaquín. International Iberian Nanotechnology Laboratory; Portugal